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C:EiAPTER 4 <br />MODELING ENDANGERED AND THREATENED-SPECIES HABITAT NEEDS <br />1. Whv Model? <br />A. Describe the usefulness of applvincr models to <br />habitat manacrement. <br />Wildlife management decisions aim at.two kinds of broad goals: <br />(1) to maintain biotic diversity, or.(2) to produce specific <br />resources for people to use and enjoy, or both.(Salwasser 1986). <br />An important assumption implied when modeling relationships <br />between wildlife.and habitat is that some aspect of populations <br />can be predicted from some aspect of habitat (Salwasser 1986). <br />To that end, wildlife manager,s and land use planners regularly <br />employ species and habitat models to help guide future management <br />decisions. The Biology Workgroup used models to depict <br />incremental changes in habitat based on incremental changes in <br />flow and other parameters, and for development of management <br />alternatives. <br />Models are simplifications of the systems they depict <br />(Schamberger and 0'Neil 1986):-- The essence of these concepts can -be applied in a model to produce some result, or to simulate a <br />desired response. Still, models that appear to be "good models" <br />can provide less than realistic predictions (Rotenberry 1986). <br />In essence, then, mathematica.l models applied to-real-world <br />situations can be used only as a tool to guide management <br />decisions having future effects on an ecosystem. In contrast, <br />models cannot be used to tell a manager what the future will look <br />like. <br />B. Describe the need to have accurate models of <br />species needs to affect successful manacrement. <br />Models may lose resolution in attaining simplicity (Schamberger <br />and 0'Neil 1986.). Models require numerous assumptions, although <br />they can never completely mimic the real world (Maynard-Smith <br />1974, Hall and Day 1977). Because of the assumptions inherent in <br />development of species/habitat models, the data used in their <br />development must be both accurate and directly applicable to the <br />geographic location being modeled. . <br />For instance, Faanes and Howard (1987) developed a model to <br />describe habitat suitability among black-shouldered kites (Elanus <br />caeruleus) in south Texas. Because of the paucity of data on the <br />species in the geographic area of conc.ern, the authors were <br />forced to use the limited data and literature available to them.